Fix scalar contraction

[mtfishman]

Closes #16.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.66%. Comparing base (840975a) to head (0061180).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #18      +/-   ##
==========================================
+ Coverage   91.17%   91.66%   +0.49%     
==========================================
  Files          16       16              
  Lines         340      360      +20     
==========================================
+ Hits          310      330      +20     
  Misses         30       30              

Flag	Coverage Δ
docs	0.00% <0.00%> (ø)

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